The present invention relates to a mobile body controlling gear and more particularly to a controlling gear suitable for the yaw axis attitude control of a mobile body such as a model helicopter, model air-craft, or the like.
In order to manipulate a model helicopter, the gyroscope (tail stabilizer) is an auxiliary device essential for stabilizing the yaw-axis control. Without the gyroscope mounted, the helicopter horizontally yaws because of no autonomous stability function to the yaw-axis.
In the yaw-axis manipulation of a model helicopter, a yaw-axis rotary motion occurs under control commands from the manipulation side to turn the nose of the helicopter in a target direction. The gyroscope can control the reciprocal control, that is, of stopping the rotation of the yaw-axis when control commands do not come from the manipulation side and of quickly rotating the yaw-axis in response to control commands from the manipulation side. In the gyroscope configuration for a model helicopter, the rotational speed of the helicopter is detected by calculating an error between a signal from an angular velocity detection sensor equipped to a model helicopter and a reference signal being an angular velocity target value. The resultant signal is transmitted to the yaw-axis control actuator of the helicopter and is subjected to feedback control to null the angular velocity of the yaw-axis.
Conventionally, the P (proportional) control system, which can provide a simplified configuration, has been employed as the feedback control method. In the P control system, the output from the controller is proportional to an error of a measurement value to a target value.
FIG. 2 is a block diagram illustrating a conventional yaw-axis controlling gear employing the P control system. Referring to FIG. 2, reference numerals 21, 23 and 11 represent addition points; 22 represents a P controller: 9 represents an actuator; 10 represents a yaw-axis driving unit; 12 represents an airframe; and 13 represents a yaw-axis angular velocity detection sensor.
A rate gyroscope or piezoelectric vibration gyroscope (piezoelectric vibration angular velocity detection sensor), for example, is used as the yaw-axis angular velocity detection sensor 13. The angular velocity signal measured by the yaw-axis angular velocity detection sensor 13 is subtracted from the angular velocity zero reference value at the addition point 21. The P controller 22 receives the resultant difference. The output of the P controller 22 is added to the yaw-axis control signal at the addition point 23. The actuator 22 receives the resultant sum. The yaw-axis driving unit 10 adjusts the pitch angle of the tail rotor in response to the output from the actuator 9, thus varying the drive force around the yaw-axis.
At the virtual addition point 11, the output from the yaw-axis driving unit 10 is added to disturbance such as a counterforce of a helicopter or wind. The resultant sum is sent to the airframe 12. The yaw-axis angular velocity detection sensor 13 detects the angular velocity around the yaw-axis of the airframe. The detected output is coupled to the addition point 21. There is a control loop (not shown in FIG. 2) which provides yaw-axis control signals by manipulating the stick of a wireless controlling gear and then transmitting remote control signals to the airframe while the operator of a wireless controlled helicopter is observing angles around the yaw-axis.
In order to perform the yaw-axis control operation in the gyroscope employing the P control system, the sensor output signal from the yaw-axis angular velocity detection sensor 13 functions as an angular velocity correction signal. The manipulation side provides a yaw-axis control signal with the opposite polarity to that of the angular velocity correction signal to the output of the P controller 22. The rotary motion of the yaw-axis occurs according to the resultant difference. The yaw-axis angular velocity detection sensor 13 handles even disturbance as the yaw-axis control signal. A rotary motion occurs proportional to the offset of an angular velocity acting as the input of the P controller 22. As a result, the conventional system has the disadvantage in that since the yaw-axis shifts due to disturbance such as side wind, it is difficult to hovers the helicopter accurately.
Recently, the PID control system built-in gyroscope for purpose of model helicopters that can cancel the offset causing the drawback of the above-mentioned P control system has been commercially introduced. The PID control system performs an integration operation for integrating existing errors and then outputting the result and a differential operation for outputting values proportional to changes in error, in addition to the proportional operation for handling the adjuster output as values proportional to the error. The differential operation is not solely used but is used to improve the proportional operation and the integration operation. For that reason, in the patent specification, the PID control system and the PID control system are handled as the same category.
FIG. 3 is a block diagram illustrating a yaw-axis controlling gear employing the PID control system. In FIG. 3, like reference numerals represent the same constituent elements as those in FIG. 2. Hence, the duplicate description is omitted here. Reference numeral 31 represents an addition point and 32 represents a PID controller.
The output signal from the yaw-axis angular velocity detection sensor 13 is added to the angular velocity zero reference value and to the yaw-axis control signal at the addition point 31. The PID controller receives the added signal and then sends the result to the actuator 9. The yaw-axis driving unit 10 receives the output from the actuator 9 and then adjusts the drive force around the yaw-axis to vary the pitch angle of the tail rotor. The virtual addition point 11 adds the output from the yaw-axis driving unit 10 to a disturbance. Then the yaw-axis driving unit 10 sends the result to the airframe 12. The yaw-axis angular velocity detection sensor 13 detects the angular velocity around the yaw-axis. The detection output is fed back to the addition point 31.
In the PID control system, the yaw-axis control signal on the manipulation side is controlled so as to offset the angular velocity zero reference value being the target value of the gyroscope. That is, the control signal is not disturbance but acts as a yaw-axis angular velocity command signal. The P control differs from the PID control in that the control signal on the manipulation side is differently operated on the gyroscope side. The PID control system can configure a very stable system because the disturbance is corrected under the I control. However, the PID system has the disadvantage in that if a degraded transient response and an abruptly-changing yaw-axis control signal are provided under the I control, the time until the motion of the yaw-axis stops is prolonged, compared with the P control. Hence, it may be considered to use a controller that can switch the status to the P control or the PID control so that the P control and the PID control is suitably selected according to the flight pattern of a helicopter.
In the P control system, it is needed to perform a trim operation at the beginning of the flight of a helicopter as initialization for stopping the yaw-axis. In this trim operation, a stable balanced state is accomplished at the neutral position of the manipulation stick on a controlling gear by moving the trim lever every manipulation contents and adding a trim correction signal from the manipulation side to a control signal. The trim correction signal is handled as a balance reference value (neutral value) of a control signal at the P control time. In FIG. 2, the reference value corresponding to the balance state is added to the addition point 21.
On the other hand, the PID control, shown in FIG. 3, does not require the trim operation under the I control because the gyroscope side performs the correcting operation. However, there is the disadvantage in that when the status is switched from the P control mode to the PID control mode, the balance reference value added in the P control operation is viewed as an angular velocity command signal from the PID control side, thus resulting in the occurrence of the yaw-axis motion.
A controlling gear that respectively uses a trim correction signal for the P control and a trim correction signal for the PID control may be employed to solve the above-described problems. However, this approach results in complicating the controlling gear and increasing the fabrication costs.